Some improvement in Precision metric docs

docs/Makefile

@@ -27,4 +27,4 @@ rebuild:
 # Catch-all target: route all unknown targets to Sphinx using the new
 # "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
 %: Makefile
-	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+	@ $(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

ignite/metrics/metric.py

@@ -219,7 +219,7 @@ def __init__(
     @abstractmethod
     def reset(self) -> None:
         """
-        Resets the metric to it's initial state.
+        Resets the metric to its initial state.
 
         By default, this is called at the start of each epoch.
         """
@@ -240,7 +240,7 @@ def update(self, output: Any) -> None:
     @abstractmethod
     def compute(self) -> Any:
         """
-        Computes the metric based on it's accumulated state.
+        Computes the metric based on its accumulated state.
 
         By default, this is called at the end of each epoch.
 
@@ -273,7 +273,7 @@ def iteration_completed(self, engine: Engine) -> None:
 
         Note:
             ``engine.state.output`` is used to compute metric values.
-            The majority of implemented metrics accepts the following formats for ``engine.state.output``:
+            The majority of implemented metrics accept the following formats for ``engine.state.output``:
             ``(y_pred, y)`` or ``{'y_pred': y_pred, 'y': y}``. ``y_pred`` and ``y`` can be torch tensors or
             list of tensors/numbers if applicable.
 

ignite/metrics/precision.py

@@ -61,8 +61,8 @@ def _prepare_output(self, output: Sequence[torch.Tensor]) -> Sequence[torch.Tens
             num_classes = 2 if self._type == "binary" else y_pred.size(1)
             if self._type == "multiclass" and y.max() + 1 > num_classes:
                 raise ValueError(
-                    f"y_pred contains less classes than y. Number of predicted classes is {num_classes}"
-                    f" and element in y has invalid class = {y.max().item() + 1}."
+                    f"y_pred contains fewer classes than y. Number of classes in the prediction is {num_classes}"
+                    f" and an element in y has invalid class = {y.max().item() + 1}."
                 )
             y = y.view(-1)
             if self._type == "binary" and self._average is False:
@@ -86,30 +86,32 @@ def _prepare_output(self, output: Sequence[torch.Tensor]) -> Sequence[torch.Tens
 
     @reinit__is_reduced
     def reset(self) -> None:
-        # `numerator`, `denominator` and `weight` are three variables chosen to be abstract
-        # representatives of the ones that are measured for cases with different `average` parameters.
-        # `weight` is only used when `average='weighted'`. Actual value of these three variables is
-        # as follows.
-        #
-        # average='samples':
-        #   numerator (torch.Tensor): sum of metric value for samples
-        #   denominator (int): number of samples
-        #
-        # average='weighted':
-        #   numerator (torch.Tensor): number of true positives per class/label
-        #   denominator (torch.Tensor): number of predicted(for precision) or actual(for recall)
-        #     positives per class/label
-        #   weight (torch.Tensor): number of actual positives per class
-        #
-        # average='micro':
-        #   numerator (torch.Tensor): sum of number of true positives for classes/labels
-        #   denominator (torch.Tensor): sum of number of predicted(for precision) or actual(for recall) positives
-        #     for classes/labels
-        #
-        # average='macro' or boolean or None:
-        #   numerator (torch.Tensor): number of true positives per class/label
-        #   denominator (torch.Tensor): number of predicted(for precision) or actual(for recall)
-        #     positives per class/label
+        """
+        `numerator`, `denominator` and `weight` are three variables chosen to be abstract
+        representatives of the ones that are measured for cases with different `average` parameters.
+        `weight` is only used when `average='weighted'`. Actual value of these three variables is
+        as follows.
+
+        average='samples':
+          numerator (torch.Tensor): sum of metric value for samples
+          denominator (int): number of samples
+
+        average='weighted':
+          numerator (torch.Tensor): number of true positives per class/label
+          denominator (torch.Tensor): number of predicted(for precision) or actual(for recall) positives per
+            class/label.
+          weight (torch.Tensor): number of actual positives per class
+
+        average='micro':
+          numerator (torch.Tensor): sum of number of true positives for classes/labels
+          denominator (torch.Tensor): sum of number of predicted(for precision) or actual(for recall) positives for
+            classes/labels.
+
+        average='macro' or boolean or None:
+          numerator (torch.Tensor): number of true positives per class/label
+          denominator (torch.Tensor): number of predicted(for precision) or actual(for recall) positives per
+            class/label.
+        """
 
         self._numerator: Union[int, torch.Tensor] = 0
         self._denominator: Union[int, torch.Tensor] = 0
@@ -120,16 +122,20 @@ def reset(self) -> None:
 
     @sync_all_reduce("_numerator", "_denominator")
     def compute(self) -> Union[torch.Tensor, float]:
-        # Return value of the metric for `average` options `'weighted'` and `'macro'` is computed as follows.
-        #
-        # .. math:: \text{Precision/Recall} = \frac{ numerator }{ denominator } \cdot weight
-        #
-        # wherein `weight` is the internal variable `weight` for `'weighted'` option and :math:`1/C`
-        # for the `macro` one. :math:`C` is the number of classes/labels.
-        #
-        # Return value of the metric for `average` options `'micro'`, `'samples'`, `False` and None is as follows.
-        #
-        # .. math:: \text{Precision/Recall} = \frac{ numerator }{ denominator }
+        r"""
+        Return value of the metric for `average` options `'weighted'` and `'macro'` is computed as follows.
+
+        .. math::
+            \text{Precision/Recall} = \frac{ numerator }{ denominator } \cdot weight
+
+        wherein `weight` is the internal variable `_weight` for `'weighted'` option and :math:`1/C`
+        for the `macro` one. :math:`C` is the number of classes/labels.
+
+        Return value of the metric for `average` options `'micro'`, `'samples'`, `False` and None is as follows.
+
+        .. math::
+            \text{Precision/Recall} = \frac{ numerator }{ denominator }
+        """
 
         if not self._updated:
             raise NotComputableError(
@@ -367,6 +373,33 @@ def thresholded_output_transform(output):
 
     @reinit__is_reduced
     def update(self, output: Sequence[torch.Tensor]) -> None:
+        r"""
+        Update the metric state using prediction and target.
+
+        Args:
+            output: a binary tuple of tensors (y_pred, y) whose shapes follow the table below. N stands for the batch
+                dimension, `...` for possible additional dimensions and C for class dimension.
+
+                .. list-table::
+                    :widths: 20 10 10 10
+                    :header-rows: 1
+
+                    * - Output member\\Data type
+                      - Binary
+                      - Multiclass
+                      - Multilabel
+                    * - y_pred
+                      - (N, ...)
+                      - (N, C, ...)
+                      - (N, C, ...)
+                    * - y
+                      - (N, ...)
+                      - (N, ...)
+                      - (N, C, ...)
+
+                For binary and multilabel data, both y and y_pred should consist of 0's and 1's, but for multiclass
+                data, y_pred and y should consist of probabilities and integers respectively.
+        """
         self._check_shape(output)
         self._check_type(output)
         y_pred, y, correct = self._prepare_output(output)